There is considerable waste of fish food supplied for feeding fish in rearing tanks, ponds in fish hatcheries and fisheries and in aquaculture fields due to undesirable characteristics of commercial fish food. Early experiments comparing meal to pelleted type feed demonstrated that many finfish utilize pelleted feed more efficiently. Many of the small meal particles were not ingested, resulting in poorer feed conversion and decreased water stability resulting in reduced water quality. This did and continues to create an unsuitable and unhealthy environment for the desired aquatic organism. To minimize these undesirable effects, many commercial feeds are processed into pellets.
However, many disadvantages exist in the pelleted feed commercially available. One major disadvantage of the commercially available feed is the high temperatures and pressures used during conventional screw-type extrusion mill processing. These harsh conditions destroy heat labile feed ingredients, such as medications, vaccines, growth promoters, vitamins, minerals and other nutrients that are advantageous, albeit necessary in many fish diets. For example, approximately 50% of vitamin C, 35% of vitamin A and 35% of thiamine are lost during commercial extrusion processing. Similar results occur for other fortifying agents during processing and storage. As a consequence, overfortification of labile nutrients in processed fish feed is currently necessary.
Efforts to provide a stable aquatic animal feed have been made. Gunter et al., U.S. Pat. No. 3,889,007 (issued Jun. 10, 1975) discloses a food composition for aquatic organisms and particularly crustaceans comprising fish meal and a fish extract, fish soluble, fish oil and a binder that may be an organic binder, such as gelatin, guar gum, agar, CMC alginate ester, collagen, and pregelatinized starch, and sea water. This feed still involves standard processing techniques, having the disadvantages of high temperatures and pressures.
Feed texture is also important for many aquatic animals. Commercially processed pelleted feed may be too hard as to be unpalatable to some fish and consequently be rejected by them. The hard pellets may also be so dense as to sink where they are not readily available to fish preferring floating feed. Conversely, the pellets may be so soft and friable that they disintegrate or dissolve too quickly. These feeds have the same disadvantages of meal feed, namely, poor feed conversion and decreased water quality due to increased growth of algae and aquatic vegetation.
Attempts have been made to increase the palatability of fish feed. For instance, Cox, U.S. Pat. No. 4,935,250 (issued Jun. 19, 1990) discloses increased palatability of fish feed pellets by coating preformed pellets with a coating of soft and flexible consistency that may be formed of alginate or guar gum set by calcium chloride solution or may incorporate gum tragacanth, pectin or gelatin.
Lastly, fishery and aquaculture management involves many different feed formulations to ensure that various types of fish are receiving proper nutrient requirements, texture and size. For instance, shrimp are particularly difficult to nourish adequately since they require a bottom (sunken) food and are raised mostly in closed water systems. As noted above, most finfish prefer floating type feed. With existing technology, a floating feed must contain starch in the feed mix to make it float. When the starch is subjected to high temperatures and pressures the starch will gleutinize or stick together. Then as the pressure on the starch is relieved, it expands trapping air in the feed. This trapped air makes the feed float. Feed produced in this way exposes the feed ingredients to high temperatures (above 220.degree. C.) and pressures (8 atmospheres). These harsh conditions destroy heat labile feed ingredients. Presently, farmers must either purchase pre-formulated commercial feed, possessing the disadvantages outlined above or must have expensive processing equipment such as extrusion mills to formulate and produce their own feed. These are very costly limitations to the fisheries and aquaculture businesses.
The aquatic animal feed of the prior art embody one or more of the disadvantageous characteristics of instability in water, inadequate nutritional value, causation of poor water quality, poor palatability or costly processing. It would be of great value to the industry to provide an alternative feed and process for producing said feed which is free of the above-mentioned disadvantages. None of the prior art compositions or processes provide all of the desirable characteristics of the stable aquatic animal feed of the present invention.